Catheter-associated bacteremia caused by Asaia lannensis in an immunosuppressed patient: a case report

Asaia spp. are an environmental Gram-negative bacterial species rarely implicated in human infections. Only a handful of cases have been reported, primarily involving catheter-associated bloodstream infections or infections related to intravenous drug abuse. We present here a case of bacteremia caused by Asaia lannensis in an immunocompromised patient with hairy cell leukemia. An 84-year-old man with a history of hairy cell leukemia presented with relapse and was treated with cladribine via a subclavian central venous catheter. The patient developed a febrile episode three weeks after the start of chemotherapy, without hemodynamic instability but with elevated inflammatory markers and a mild erythema at the catheter site. Blood cultures drawn both by venipuncture and from the catheter grew a slow-growing, thin Gram-negative bacillus after prolonged incubation. Conventional identification methods based on biochemical profiling misidentified the bacterium as Serratia fonticola, and MALDI-TOF MS analysis was inconclusive. After initial genus-level identification through 16 S rDNA gene sequencing, whole genome sequencing demonstrated the classification to Asaia lannensis. The same organism was cultured directly from the catheter, confirming the source of infection. Antimicrobial susceptibility testing revealed elevated MICs to most commonly-used antibiotics, including beta-lactams, macrolides, quinolones, and last-resort agents such as colistin and cefiderocol. However, lower minimal inhibitory concentrations were observed for aminoglycosides and tetracyclines, suggesting potential in vitro activity. The patient showed rapid clinical improvement after catheter removal and a short antibiotics course, with no recurrence of fever or hemodynamic deterioration. This clinical observation is singular in that Asaia lannensis was recovered both from blood cultures and directly from the catheter, confirming the device as the source of infection. This case illustrates the potential of Asaia lannensis to cause clinically-significant infections in immunocompromised patients, particularly those with central venous catheters. It highlights the limitations of conventional microbiological identification techniques when dealing with uncommon environmental pathogens. Catheter removal was crucial to resolution, underscoring the importance of device management in the treatment of catheter-associated bloodstream infections. Clinicians and microbiologists should remain alert to rare opportunistic organisms in patients with indwelling medical devices and consider advanced molecular diagnostics when standard methods fail.